Multipactor suppression in dielectric-assist accelerating structures via diamondlike carbon coatings

Mori, Shigeo; Yoshida, Mitsuhiro; Satoh, Daisuke

doi:10.1103/physrevaccelbeams.24.022001

Cited by 10 publications

(9 citation statements)

References 15 publications

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“…( 5) and Boris method agree perfectly with each other, a fact that allows us to justify and validate the simplification made in the third equation of the system (2) of disregarding the term proportional to the magnetic field H 0 . The analytical approximation (6) gives reasonable values for the electron trajectory, although the fact that its validity is restricted to very small times means that as time goes by the approximate trajectory differs from the full equation (5). In Fig.…”

Section: A Down Zonementioning

confidence: 90%

“…In Fig 6 e) the time taken for the electron to hit the walls is plotted normalised to the RF period and expressed as a function of the initial phase of the field. The results have been plotted using for this calculation the equation of the radial trajectory (5), referred to in the legend as exact analytical, and the approximation of this equation for small times t/T << 1 (7). Eq.…”

Section: A Down Zonementioning

confidence: 99%

“…The advantage of the DAA structure is that it has an extremely high quality factor and a very high shunt impedance at room temperature since the electromagnetic field distribution of the accelerating mode T M 02 reduces greatly the losses on the metallic wall as compared to that of a T M 01 mode of the pillbox cylindrical cavity. Several DAA designs have been presented in the literature, and even some prototypes have been build and tested [4], [5], [6]. Although their good performance in terms of quality factor and shunt impedance has been demonstrated with measurements, it has also been found that DAA structures suffer multipactor during operation.…”

Section: Introductionmentioning

confidence: 99%

“…So far, the maximum accelerating field of DAA cavities has been limited to a few MV/m by discharges. In [5], it is stated that in the DAA cavity, with the nominal Secondary Electron Yield (SEY) of the dielectric, the multipactor limits the maximum accelerating gradient to about 1 or 2 MV/m. If a low-SEY coating is applied to the dielectric, they found that the gradient can be increased up to 12 MV/m.…”

Section: Introductionmentioning

confidence: 99%

“…However, they also state that for the application of the DAA cavity to the accelerator facility, a higher accelerating gradient would be required, e.g., 30 MV/m. To the Authors' knowledge, the risk of multipactor occurrence in the DAA structure described in [5] was not taken into account during its design. Then, after fabrication of the prototype it was found that the multipactor was a major concern for good performance and, even with the application of the low-SEY coating, the maximum gradient was still limited by discharges.…”

Section: Introductionmentioning

confidence: 99%

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Analytical RF Pulse Heating Analysis for High Gradient Accelerating Structures

Gonzalez-Iglesias

Esperante

Gimeno

et al. 2021

IEEE Trans. Nucl. Sci.

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The main aim of this work is to present a simple method, based on analytical expressions, for obtaining the temperature increase due to the Joule effect inside the metallic walls of an RF accelerating component. This technique relies on solving the 1D heat transfer equation for a thick wall, considering that the heat sources inside the wall are the ohmic losses produced by the RF electromagnetic fields penetrating into the metal with finite electrical conductivity. Furthermore, it is discussed how the theoretical expressions of this method can be applied to obtain an approximation to the temperature increase in realistic 3D RF accelerating structures, taking as an example the cavity of an RF electron photoinjector and a travelling wave linac cavity. These theoretical results have been benchmarked with numerical simulations carried out with a commercial Finite Element Method (FEM) software, finding good agreement among them. Besides, the advantage of the analytical method with respect to the numerical simulations is evidenced. In particular, the model could be very useful during the design and optimization phase of RF accelerating structures, where many different combinations of parameters must be analysed in order to obtain the proper working point of the device, allowing to save time and speed up the process. However, it must be mentioned that the method described in this manuscript is intended to provide a quick approximation to the temperature increase in the device, which of course is not as accurate as the proper 3D numerical simulations of the component.

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Section: A Down Zonementioning

confidence: 90%

Section: A Down Zonementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Analytical RF Pulse Heating Analysis for High Gradient Accelerating Structures

Gonzalez-Iglesias

Esperante

Gimeno

et al. 2021

IEEE Trans. Nucl. Sci.

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Non-resonant ultra-fast multipactor regime in dielectric-assist accelerating structures

González-Iglesias,

Gimeno,

Esperante

et al. 2024

Results in Physics

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Effect analysis of angular momentum on coaxial multipactor with 1D3V statistical modeling

Lin

Wong

et al. 2022

Physics of Plasmas

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How does the multipactor threshold voltage vary when two semi-infinite parallel plates are bent into coaxial lines? This topic with respect to the geometric effect on multipactor formation is essential for the optimal design of multipactor-free microwave systems. It requires accurate multipactor threshold analysis of the coaxial lines with the consideration of electron angular momentum, which is not considered in most multipactor theoretical approaches for efficient threshold calculations. To address this effect from the perspective of multipactor threshold analysis, this work presents an improved implementation of the multipactor statistical modeling (1D3V modeling) by constructing the joint probability density function with angular emissions and impacts of secondary electrons included. On that basis, a multipactor susceptibility chart of coaxial lines is conducted and compared with the experimental results, and multipactor threshold voltage for varying ratios of outer to inner conductor radii (radius ratio) is calculated to quantitatively investigate the effect of electron angular momentum. The results indicate that the 1D3V modeling can achieve fairly good agreement with the experimental result and relatively better accuracy of threshold calculation at first multipactor orders with comparison to the 1D1V result which only regards the radial momentum. With different variations of the threshold voltage from the 1D1V result, the 1D3V result reaches its minimum at a specific radius ratio before the sudden rise, and the discrepancy becomes more significant for the high-order multipactor, revealing the indispensable effect of angular momentum on the coaxial multipactor. The intricacies of the mechanism analysis will be further explored in the paper.

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Multipactor suppression in dielectric-assist accelerating structures via diamondlike carbon coatings

Cited by 10 publications

References 15 publications

Analytical RF Pulse Heating Analysis for High Gradient Accelerating Structures

Analytical RF Pulse Heating Analysis for High Gradient Accelerating Structures

Non-resonant ultra-fast multipactor regime in dielectric-assist accelerating structures

Effect analysis of angular momentum on coaxial multipactor with 1D3V statistical modeling

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